Waste materials, especially municipal wastes containing a complex variety of components including magnetic metal; non-magnetic, conductive metals; non-magnetic, non-conductive metals*; organic materials, such as plastics, vegetable matter, animal matter and the like; and non-metallic inorganic materials, such as glass, ceramic materials, earth, rock and the like. Various methods have been developed for separating these components into their component parts. For example, elutriation methods have been utilized to separate organic materials from the inorganic materials. Air tables have been employed to recover heavy metals. Air classifiers have been employed to separate the low density materials from the high density materials. Magnetic fields have been utilized to separate the magentic metals from non-magnetic materials. Each of these methods has its merits, but to the applicants' knowledge, there is no method besides the present process that accomplishes the separation of non-magnetic, conductive metals from a mixture, containing non-magnetic, conductive metals; non-magnetic, non-conductive metals; organic materials and non-metallic inorganic materials. FNT For purposes of this invention, non-magnetic, non-conductive metals are non-ferrous magnetic metals that are relatively poor electrical conductors as compared for example, to aluminum, copper, silver and the like. Typical non-magnetic, non-conductive metals include lead, austenitic stainless steel, titanium and nickel.
The objective of the present invention is to separate from a particulate mixture of materials the non-magnetic conductive metals (NC metals herein) in a size range of approximately 4 mesh to 12" or larger. The device described for that separation employes a linear motor which causes the separation of NC metals from non-magnetic, non-conductive materials.
The linear motor, when operating, generates a travelling magnetic field down the motor's length. When a particulate mixture is passed over the motor, eddy currents are induced in the non-magnetic conductive metals. The eddy currents generate a magnetic field in the metal that interacts with the moving field generated by the motor, and draws the NC metals along the linear motor force field. When the motor is arranged, and draws the NC metals away from the body of the mixture, a separation is achieved.
The use of eddy currents for separating aluminum (especially) from other metals or nonmetals is not new. In 1965 Eriez Magnetics developed an eddy current separator using permanent magnets mounted on a wheel underneath a table to induce the field and metal movement (See Nov. 1, 1965 issue of CSEN, pg. 125). Vanderbilt University developed a process using a single stationary magnet and conveys a particulate mixture through the magnetic field. The aluminum and some other nonferrous are deflected from entering the field. Vanderbilt has also built a travelling wave separator designed to exert forces on metals by sweeping a "pulse" past the sample. The pulse is generated by a linear array of electromagnets, each being briefly turned on in succession so as to move the pulse from one end to the other. (See the 1971 Annual Report on Magnetic Separation of Non-Ferrous Metal, Vanderbilt University, Department of Physics and Astronomy).
The use of a linear motor to generate a moving magnetic field for the required separation is unique and offers many advantages -- high strength, low cost, low power costs, simple construction, and a flexibility for separator design not available with other systems.